High temperature bis(epoxyalkyl) carborane adhesives

ABSTRACT

The process of providing an adhesive junction between two workpieces having opposing smooth surfaces comprising the steps of mixing material selected from the group consisting of bis(epoxybutyl)carborane, bis(epoxypentyl)carborane, and bis(epoxyhexyl)carborane, with a curing agent selected from the group consisting of boron trifluoride ethylamine and 4,4&#39;&#39;diaminodiphenylsulfone, applying said mixture to the opposing surfaces, joining the surfaces and allowing the workpieces with the mixture therebetween to harden under heat and pressure.

United States Patent Barnes et al.

HIGH TEMPERATURE BIS(EPOXYALKYL) CARBORANE ADHESIVES Inventors: Robert L. Barnes, Clifton; Daniel Grafstein, Morristown, both of NJ.

Assignec: The Singer Company, New York, NY.

Filed: Sept. 25, 1968 Appl. No.: 762,614

U.S. Cl ..260/348 R, 260/606.5 B, 260/2 N,

156/325 Int. Cl. ..C07d 109/02, C07d 107/02 Field of Search ..260/606.5 B, 348

References Cited UNITED STATES PATENTS 4/1966 Green et a1. ..260/606.5

Dupont et al. ..260/348 Grafstein et al ..260/348 X Primary ExaminerNorma S. Milestone AttorneyS. A. Giarratana, G. B. Oujevolk and S. M. Bender [5 7] ABSTRACT The process of providing an adhesive junction between two workpieces having opposing smooth surfaces comprising the steps of mixing material selected from the group consisting of bis(epoxybutyl)carborane, bis(epoxypentyl)carborane, and bis(epoxyhexyl)carborane, with a curing agent selected from the group consisting of boron trifluoride ethylamine and 4,4- diaminodiphenylsulfone, applying said mixture to the opposing surfaces, joining the surfaces and allowing the workpieces with the mixture therebetween to harden under heat and pressure.

6 Claims, N0 Drawings HIGH TEMPERATURE BIS(EPOXYALKYL) CARBORANE ADHESIVES The invention described herein was made in the perforrnance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

The present invention relates to the preparation of bis(epoxyalkyl)carborane monomers, alkenyl intermediates leading to these monomers, and formulations based on these monomers which are useful for room temperature and hightemperature adhesive application.

Generally speaking, bisalkenylcarborane intermediates which are the subject of the present invention having the following structure the isomeric compound 1,7-bis(3-butenyl)-neocarborane.

These compounds can be converted to the corresponding terminal epoxy derivatives having the following structure The following compounds are also characterized herein:

(a) z 1 1,2-bis (epoxypropyl) carborane (b) a; 2; 1, 2-bis (epoxybutyl) carborane (c) a: 3; 1, 2-bis (epoxypentyl) carborane Ed; 1: 4; 1, 2-bis (epoxyhexyl) carboranc the isomeric compound 1,7-bis(ep0xybutyl)- neo-earborane.

These epoxies can be cured to hard solids by catalysts and/or reactive hardeners to form a polymer having the following repeating unit in its general structure.

The synthesis of carborane C B l-l which is the base material for the present invention has been described in a series of articles appearing in the 1963 December issue of Inorganic Chemistry.

Carborane can be converted to a series of bis( alkenyl)-carboranes using a dilithium derivative in accordance with the following reactions:

C Li 2R-II Bio ic EXAMPLE 1 l,2-Bis(3-butenyl)carborane: x=2

A slight excess of 1.6M butyllithium solution in hexane 135 ml or 0.216 moles of BuLi) was transferred to a dropping funnel in a nitrogen-filled glove bag. The solution was added over a 15-minute period, with stirring, to ll.5g (0.0800 moles) of carborane dissolved in 75 ml of anhydrous ethyl ether contained in a round bottom reaction flask. During addition, a nitrogen flow was maintained over the system, and the flask was cooled with an ice-water bath. After addition was complete, the suspension of heavy white solid was stirred at room temperature for one hour. The suspension was allowed 5 to settle, and the bulk of the supernatant liquid was removed with a syringe. About 75 ml of anhydrous ethyl ether was added to the system with stirring to wash the solid. The bulk of the solution was removed, and the procedure was repeated. About ml of anhydrous ethyl ether was added, and the mixture was heated to reflux. A weighed quantity of 4-bromol-butene (27.0g 0.200 moles) was added to the system over a 10-minute period. After a two-hour reflux period, the reaction mixture was poured into 200 ml of water and thoroughly mixed. The ether layer was separated and dried with magnesium sulphate. The crude product, obtained from the removal of the ether solvent on a rotary evaporator, was fractionally distilled under vacuum (0.1 mm) and the fraction which evolved at a head temperature of l50-l70 C was collected and crystallized. The colorless solid (14.3g representing a 76 percent conversion of carborane to desired product) had a m.p. range of 70-72 C. Gas chromatographic and infrared analyses indicated that the sample was 98 percent pure and an elemental analysis was in excellent agreement with the expected values.

Calcd. for B, C, l-l :l3,42.8;C,47.7;H,9.5 Found: B,42.4;C,48.2;l-l,9.5

EXAMPLE 2 EXAMPLE 3 l,2-Bis(5-hexenyl)carborane: x=4

The procedure described above for the preparation of bis(butenyl)carborane was followed using the following amounts of reagents.

150 ml butyllithium solution (0.240 moles of BuLi) 14.4g carborane (0.100 moles) 32g 6-bromo-l-hexane (0.20 moles) The crude product was distilled under vacuum (0.] mm) and the fraction which evolved at a head temperature of 180 C was collected 268g of colorless liquid representing a conversion of 87 percent carborane to desired product). Gas chro matographic and infrared analyses indicated that the product was 96 percent pure.

EXAMPLE 4 l ,2'Bis( 2-propenyl )carborane: x=l

The procedure described above for the preparation of bis( butenyl)carborane was followed except that a longer reflux time (24 hours) was employed. The following amounts of reagents were used.

150 ml butyllithium solution (0.240 moles BuLi) 14.4 g carborane (0.100 moles) 29g allylbromide (0.24 moles) The crude product was distilled under vacuum (0.1 mm) and the product which evolved at a head temperature of l50 C was collected (40 g of a colorless liquid representing a conversion of 18 percent carborane to desired product. Gas chromatographic and infrared analyses indicated that the sample was 93 percent pure.

EXAMPLE 5 l ,7-Bis( 3butenyl)-neo-carborane: x=2

The procedure described above for the preparation of bis(butenyl)carborane was followed except that the intermediate step involving purification of dilithio-neo-carborane was omitted. The following amounts of reagents were used.

50 ml butyllithium solution (0.800 moles of BuLi) 5.8g carborane (0.040 moles) l0.8g 4-bromo-l-butene (0.795 moles) The crude product was distilled under vacuum (0.1 mm) and the fraction which evolved at a head temperature of 150 C was collected (6.2 g of a colorless liquid representing 60 percent conversion of carborane to desired product). Gas chromatographic and infrared analyses indicated that the product was 93 percent pure.

Bis(alkenyl)carboranes could be converted to the corresponding terminal bis(epoxyalkyl)carborane monomers by treatment with trifluoroperacetic acid under carefully controlled buffer conditions in the following manner EXAMPLE 6 l ,2-Bis( epoxybutyl)carborane: x=2

Trifluoroperacetic acid was prepared in the following manner. Sixty ml of methylene chloride was added to 4.4 ml (0.16 moles) of 90 percent hydrogen peroxide at 0 C. A total of 22.8 ml (0.160 moles) of trifluoroacetic anhydride was added to the above solution with stirring over a ten-minute period. Stirring was continued for another 10 minutes. A mixture of 100 ml of methylene chloride, 36g of sodium carbonate and 13.2g (0.0520 moles) of bisbutenylcarborane was placed in a three-necked round bottom flask. The flask was equipped with a mechanical stirrer, reflux condenser and a dropping funnel. The solution of trifluoroperacetic acid was added dropwise over a -minute period. During this time, the temperature of the reaction was maintained below reflux by the use of an ice-water bath. After the addition was complete, the mixture was refluxed for 30 minutes. Following the reflux period, reaction of a drop of the supernatant liquid to starchiodide paper was negative. indicating the absence of peroxides. Gravity filtration of the reaction mixture followed by removal of solvent from the filtrate on a rotary evaporator gave 4.1g of a white solid. The sample was distilled under vacuum and the fraction which evolved at a head temperature of 200 C was collected and crystallized. The colorless solid( 10g representing a 67 percent conversion of alkenylcarborane to desired product) had a melting point range of 68- 71C. Gas chromatographic and infrared analyses indicated that the sample was better than percent pure and an elemental analysis was in excellent agreement with the calculated values.

Calcd. for B, C l-l O :B,38.0:C,42.3;H,8.5 Found: B,38.6:C,42.5;H,8.6

EXAMPLE 7 l ,2-Bis( epoxypentyl)carborane: x=3

The procedure used for the preparation of bis(epoxybutyl)- carborane was followed using the following amounts of reagents.

2.2 ml 90 percent Hydrogen Peroxide (0.080 moles) l 1.4 ml Trifluoroacetic Anhydride (0.080 moles) 6.5g 1,2-Bis(4-pentenyl)carborane (0.021 moles) The crude product was distilled under vacuum (0.1 mm) and the fraction which evolved at a head temperature of 200C was collected and crystallized. The colorless solid (5g representing a 68 percent conversion of carborane to desired product) had a melting point range of 68-75 C. Gas chromatographic and infrared analyses indicated a purity of 95 percent and an elemental analysis was in excellent agreement with the theoretical values.

Found: B,33.3;C,45.3;H,9.1

EXAMPLE 8 l,2-Bis(epoxyhexyl)carborane: x=4

The procedure used for the preparation of bis(epoxybutyl)- carborane was followed using the following amounts of reagents.

4.4 ml of 90 percent Hydrogen Peroxide (0.16 moles) 22.8 ml of Trifluoroacetic Anhydride (0.160 moles) l3.6g. of 1,2-Bis(5-hexenyl)carborane) (0.043 moles) The crude product was distilled under vacuum (0.1 mm) and the fraction (10.5g representing a conversion of 73 percent of alkenylcarborane to desired product) which evolved at a head temperature of 225 C was collected. Gas chromatographic and infrared analyses of the colorless liquid indicated a purity of 97 percent. An elemental analysis was in excellent agreement with the calculated values.

Calcd. for B, C,,,l-l O B,32.8; C,49.5; l-l,9.4

EXAMPLE 9 l,2-Bis(epoxypropyl)carborane: .x=l

The procedure used for the preparation of bis( epoxybutyl)- carborane was followed except that disodium hydrogen phosphate was used as the buffer in place of sodium carbonate. The following amount of reagents were used:

2.2 ml of Hydrogen Peroxide (0.080 moles) l 1.4 ml of Trifluoroacetic Anhydride (0.080 moles) 3.5g of l,2-Bis( 2-propenyl)carborane (0.016 moles) A total of 3.0g of product (representing an 83 percent conversion of alkenylcarborane to desired product) was isolated. Gas chromatographic and infrared analyses of the solid (melting point 36-48 C) indicated a purity of 97 percent.

EXAMPLE l ,7-Bis( epoxybutyl)-neo-carborane: x=2

The procedure used for the preparation of bis( epoxybutyl)- carborane was followed using the following amounts of reagents.

2.2 ml of 90 percent Hydrogen Peroxide (0.080 moles) l 1.4 ml of Trifiuoroacetic Anhydride (0.080 moles) 6.6g of l ,7-Bis(butyl)-neo-carborane (0.026 moles) The crude product was distilled under vacuum (0.l mm) and the fraction evolved at a head temperature of l50-l 70 C was collected and crystallized. The colorless solid (4.5g representing a conversion of 68 percent of alkenyLneo-carborane to desired product) had a melting point range of 5 l-54 C. Gas chromatographic and infrared analyses of the product indicated a purity of 94 percent.

Adhesive Properties Example Lap-Shear Epoxy Number Strength, psi

Bis( epoxybutyl )carborane 12 2320 Bis( epoxypentyl)carborane I3 2810 Bis( epoxyhexyl )carborane I4 3600 Representative lap-shear strengths at room temperature are listed below for the epoxies cured with the reactive hardener 4,4'-diaminodiphenylsulfone.

Example Lap-Shear Epoxy Number Strength, psi

Bis( epoxypropyl )carborane 15 1740 Bis( epoxybutyl )carborane 16 2040 Bis( epoxybutyl )-neo-carborane 17 2000 Lap-shear strengths at 400 C (air atmospheres-l0 minute hold at temperature) as high as 980 psi have been obtained with the bis(epoxybutyl)carborane-3phrBF zEtNH catalyst system Example 18.

Superior high temperature results are obtained by reacting the bis(epoxyalkyl)carboranes with certain reactive hardeners. Lap-shear strengths as high as 1,730 psi have been obtained at 500 F in air when bis(epoxybutyl)carborane was cured with 4,4-diaminodiphenylsulfone (Example Number 19). These values, which represent 80 percent retention of room temperature strength (2,040 psi) were obtained on samples which had been previously soaked at 500 F for 2 hours. Lap-shear strengths as high as 1,460 psi at 500 F in air have been obtained on samples soaked at 500 F for 24 hours (Example Number 20). At 440 F, 100 percent of room-temperature lap-shear strength is retained (Example Number 21 The following examples relate to preparation of lap-shear test specimens, testing procedures, formulations for the various adhesive compositions and test results.

EXAMPLE 1 1 Preparation of Lap-shear Specimens and Testing Procedures Stainless steel strips (17-7) were cut to dimensions called for in Mil Spec MIL-A-005090E (Wep) for lap-shear specimens (5.094 in. X 1.00 in. X 0.050 in.). All the edges were de-burred. The strips were first degreased in methylethylketone prior to a ten-minute immersion in an acid solution at room temperature. This acid solution had the following composition.

Nitric Acid (70%) 10% Hydrofluoric Acid (50%) 2% Water 88% On removal from the acid solution, the adherends were thoroughly rinsed with cold water and then immersed in a chromic acid solution for 10 minutes at 160 F. The composition of the acid solution was as follows:

Sodium Dichromate 28.5g Sulphuric Acid 285g Tap Water To make 1 liter Aluminum Metal 5g After the acid treatment, the adherends were thoroughly rinsed in cold running tap water. Finally, they were rinsed in distilled water, observed to make sure they held a continuous film of water, and dried in an oven for 30 minutes at 160 F. After the degreasing step, all handling was done using cotton gloves,

The adherends were laid up in a special mounting fixture which ensured accurate alignment of the adherends and an exact overlap of 0.50 in. The fixture could take a total of five specimens (ten adherends). The B-staged epoxy was warmed (2l200 F depending on the test sample) are carefully applied to the adherends. The latter were then warmed with an air gun and the liquid was spread over the overlap surfaces, In some cases, the fixture was placed in a vacuum oven at 212 F for 15-20 minutes to outgas dissolved air in the epoxy. A 0.5 inch wide strip of glass cloth (Volan A-18l or l 12) was laid over the overlap area of the lower adherend, and the upper ad herend was then placed over the glass cloth. The lay-up fixture containing the specimens was placed in a Carver Hydraulic Press equipped with heating plates and a modified quick closer attachment to ensure constant pressure. After curing, the specimens were removed from the mounting fixture and filed to remove excess epoxy. The glue line thickness in each specimen was determined by measuring the thickness of each adherend adjacent to the overlap area with a micrometer, followed by measuring the total thickness at the overlap area. A simple subtraction gave the glue line thickness. All specimens were tested in an lnstron Tensile Tester at a constant strain rate of 0.01 in./in./min. In elevated temperature tests, a specially designed furnace was preheated and placed around the specimen in the lnstron Tensile Machine. A period of 15 to 20 minutes was required to bring the specimens to the test temperature. The specimen was held at that temperature for ten minutes and tested (at temperature).

EXAMPLE 12 Lap-shear Strength Bis( epoxybutyl )carborane-3phrBF- zEtNH Composition-1.86 g epoxy 0.06g catalyst B-stage230-265F for 50 minutes OutgassedNo Glass ClothStyle l8l Cure-Assembly445 F, psi, 1 hour Post-CureNone EXAMPLE 1 3 Lap-shear Strength Bis(epoxypentyl)carborane-liphrBF itNl-h Test Glue Line Failure Strength Temperature F Thickness (in.) psi Composition-1.0g epoxy 0.030g catalyst B-stage225-260F for 30 minutes OutgassedNo Glass ClothStyle l8l Cure-Assembly-445 F, 120 psi, 1 hour Post-Cure-None EXAMPLE l4 Lap-shear Strength Bis( epoxyhexyl)carborane-3phrBF zEtNll Test Glue Line Failure Strength Temperature F Thickness (in.) psi Composition-1.023 epoxy 003g catalyst B-stage230-26S F for 30 minutes Outgassed-No Glass Cloth-Style l8l Cure-Assembly445 F, 120 psi, 1 hour Posbcure-None EXAMPLE l5 Lap-shear Strength Bis( epoxypropyl )carborane-48phr 4,4-

diaminodiphenylsulfone Test Glue Line Failure Strength Temperature "F Thickness (in.) psi Composition-152g epoxy 0.73g hardener B-stage-SOO F for 40 minutes Outgassed-Yes Glass Cloth-Style 12 Cure-Assembly-390" F, 120 psi, 2% hours EXAMPLE l6 Lap-shear Strength Bis( epoxybutyl )carborane-47phr 4,4- diaminodiphenylsulfone Test Glue Line Failure Strength Temperature "F Thickness (in.) psi Composition- 1 .5 lg epoxy 07 lg hardener B-stage300 F for 40 minutes Outgassed-Yes Glass Cloth-Style 112 Cure-Assembly-390 F, 120 psi, 2% hours Post-Cure-None EXAMPLE l7 Lap-shear Strength Bis(epoxybutyl)-neo-carborane-28 phr 4,4-

diaminodiphenylsulfone Test Glue Line Failure Strength Temperature F Thickness (in.) psi Composition-2.023 epoxy 0.56g hardener B-stage-300 F for 2% hours. Specimens l-l Specimens l l-l received an additional 3 hours post-cure at 300 F Outgassed-Yes Glass Cloth-Style l8] Cure-Assembly445 F, 120 psi, 2 hours Composition-2.0 lg epoxy 0.063 catalyst B-stage2l2 F for 1 hour Outgassed-Yes Glass Cloth-None 2o Cure-Assembly-445 F, 120 psi, 1 hour Post-Cure-None EXAMPLE 1 9 Lap-shear Strength Bis( epoxybutyl )carborane-47phr 4,4 diaminodiphenylsulfone Test Glue Line Failure Strength Temperature F Thickness (in.) psi 500 0.006 1730 Composition- 1 ,5 lg epoxy 0.71 g hardener B-state300 F for 40 minutes 3 5 Outgassed-Yes Glass Cloth-Style 112 Cure-Assembly390 F, 120 psi, 2% hours Post-Cure500 F for 2 hours 40 EXAMPLE 20 Lap-shear Strength Bis( epoxybutyl )carborane-48phr 4,4- diaminodiphenylsulfone Test Glue Line Failure Strength Temperature F Thickness (in.) psi 500 0.004 1460 50 Composition-L51 g epoxy 0.73g hardener Estate-300 F. for 45 minutes Outgassed-Yes Glass Cloth-Style H2 Cure Assembly390 F, 120 psi, 2 hours Post-Cure-24 hours at 500 F EXAMPLE 21:

Lap-shear Strength Bis(epoxybutyl)carborane-30phr 4,4-

diaminodiphenylsulfone Test Glue Line Failure Strength Temperature "F Thickness (in.) psi Composition-2.02g epoxy 0.60g hardener B-stage226302 F for 60 minutes followed by 300 F for minutes Outgassed- Yes Glass Cloth-Style l8l Cure Assembly-445 F, psi, 2 hours Post-Cure-None We claim: 75 l. l,2-Bis( epoxyalkyhcarborane of the following structure xo m where z=1, 2, 3, and 4 

2. 1,2-Bis 2,3epoxypropyl) carborane.
 3. 1,2-Bis (3,4epoxybutyl) carborane.
 4. 1,2-Bis (4,5epoxypentyl carborane.
 5. 1,2-Bis (5,6epoxyhexyl) carborane.
 6. 1,7-Bis (3,4epoxybutyl)-neo-carborane. 